Probing relic neutrino decays with 21 cm cosmology

TL;DR

This paper explores how 21 cm cosmology can be used to test relic neutrino decays, deriving constraints from EDGES data and proposing explanations for observed anomalies through neutrino decay scenarios.

Contribution

It introduces a method to constrain relic neutrino decay lifetimes using 21 cm observations and links these to anomalies like EDGES and ARCADE 2, correcting previous theoretical expressions.

Findings

Constraints on neutrino decay lifetimes from EDGES data.

Potential explanation of EDGES and ARCADE 2 anomalies via neutrino decays.

A corrected formula for the intensity calculation at relevant redshifts.

Abstract

We show how 21 cm cosmology can test relic neutrino radiative decays into sterile neutrinos. Using recent EDGES results, we derive constraints on the lifetime of the decaying neutrinos. If the EDGES anomaly will be confirmed, then there are two solutions, one for much longer and one for much shorter lifetimes than the age of the universe, showing how relic neutrino radiative decays can explain the anomaly in a simple way. We also show how to combine EDGES results with those from radio background observations, showing that potentially the ARCADE 2 excess can be also reproduced together with the EDGES anomaly within the proposed non-standard cosmological scenario. Our calculation of the specific intensity at the redshifts probed by EDGES can be also applied to the case of decaying dark matter and it also corrects a flawed expression appeared in previous literature.